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On 26/08/05, Steve Bliss <steve.bliss@sbcglobal.net> wrote:
> In lugnet.animation, James Reynolds wrote:
> > Second, if he (or someone else) does pay heed to this thread, I want to
> > discourage extending the LDraw file format to include time info or creating
> > a
> > brand new format from scratch.
>
> If we followed that logic, LDraw would never have existed in the first place.
> When LDraw started out, there were already plenty of 3D modeling systems.
> Heck,
> there were already lego-brick subsets of 3D modeling systems.
>
> Yet LDraw does exist, and it seems to be a useful thing to have.
>
> I think a big part of the reason LDraw has survived and thrived is because of
> the simplicity of the file format. Implementing an LDraw renderer is a
> 'relatively' simple process (if you've got a graphics package handy), so more
> people are encouraged to write programs to work with the LDraw format. But
> LDraw doesn't allow all the powerful operations of POV-Ray.
>
> Likewise, an LDraw-based animation wouldn't have all the power of POV-Ray.
> But
> it would be simple, and could do basic things. So maybe an LDraw-based
> 'minifig
> walk' would have a minifig twiddling its legs. But for a lot of people, that
> would be sufficient. And people who want more, would go on to animating in
> POV-Ray.
>
> Steve
In this context - a very simple or basic extension language could be
used to add an animation block with keyframe/timecode information.
Then, when you need to break out the big guns, you can embed POV code
into it for complex techniques. The code is interpreted by the output
exporters so that each part in the MPD (and certain subparts) become
POV named structures (I cannot remember the syntax, but I remember
doing that in POV) with the same names or references as used in the
timebase. This would give a combination of simplicity, extensibility
(programs that dont want to deal with it just ignore the tags, and
write them back out, possibly flagging that they may need
regeneration), and huge flexibilty or complexity if you need that.
Embedding languages in others is a well known technique, and things
like that do exist in some of the pro animation packages. Only here -
because we are intending to render out to POV, it is even easier to
embed it, as long as you get your identifiers correct. The GUI could
then offer a basic notepad widget to edit those in.
To handle this in LDraw as it is now - you would have to probably use
a metacommand, and then prefix every line of the embedded block with a
metacommand - which would work, but be a little ugly. Again though - a
GUI could wrap this away, and give you a text editor which
automatically deals with meta-command generation.
<contraversial>
One problem with LDraw is that extending it can sometimes be awkward
(multi-line extensions), and it is one reason that I have though that
a modern XML style file format based upon LDraw would give more
extensibility.
</contraversial>
I have to agree here with Steve, LDraw and the tools around it didnt
get where it is by having its head in the sand - it changed, and there
may be cases in the future for it to change in other ways.
OrionRobots
--
http://orionrobots.co.uk - Build Robots
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